Add visitors section

Author: adriaandotcom

_docs/33_explained/05_uniques.md

@@ -38,6 +38,10 @@ A direct visit occurs when a user lands on your website by typing the URL into t
 
 ![](/images/direct-visit.jpg)
 
+## Some pages have pageviews but (almost) no visitors
+
+This happens when users navigate within your website. After the first visitor is recorded, any additional pageviews during the session are counted as pageviews, not visitors. For example, if someone clicks through multiple pages on your site, those are additional pageviews but not visitors.
+
 ## SPAs
 
 If you have a single-page application we automatically see all visits after the first visit as a non unique visit. For the first visit we use above functionality to detect if a visit is unique.